To form individual semiconductor devices from a semiconductor wafer, various features such as transistors, storage capacitors, and other electronic circuitry are formed on the front of the semiconductor wafer, then the wafer is diced or singulated (singularized) to form a plurality of individual semiconductor dice.
One method to dice a semiconductor wafer is to attach a plasticized adhesive tape or film to a frame, adhere the semiconductor wafer to the adhesive film, and then cut through the wafer from the circuit (front) side with a wafer or dicing saw at a wafer scribe (kerf or “street”) area and partially into the adhesive film to ensure complete singulation of each semiconductor die. Each die which has been determined to be functional from a prior probe test is then removed from the adhesive film for packaging.
Semiconductor devices having small outlines and thin profiles are desirable to minimize the size of electronic devices such as notebook computers, cell phones, and generally any device into which they are installed. However, processing semiconductor devices on a very thin semiconductor wafer is difficult because an already fragile semiconductor wafer becomes even more susceptible to breakage as it becomes thinner.
Methods of wafer singulation which aid in the formation of very thin semiconductor devices have been proposed. In one method, electronic circuitry is formed on a relatively thick semiconductor wafer, then grooves are only partially cut into the front of the semiconductor wafer at the scribe areas. Subsequently, the wafer is etched or ground from the back of the wafer to the level of the cuts. Back grinding the wafer first thins it to a desired profile, then dices the wafer once the level of the cuts is reached.
To minimize the outline of a semiconductor device, attempts have been made to stack a plurality of semiconductor dice. While this increases the thickness of a completed device, it is sometimes preferable to have a thicker package than to increase the overall outline or “footprint” of the device. Stacking semiconductor device requires electrical interconnections from one device to another, which is often performed through an interconnection running along the outside of the dice, or through vias which have been etched from the front through the dice prior to their singulation from the wafer. Vias through the wafer are formed by mechanically or chemically etching completely through the wafer from the front. A conductor, typically metal, is then formed within the opening through the wafer usually by chemical vapor deposition (CVD) or by reflow of a metal.
A method which allows for improved processing of a semiconductor device would be desirable.